Consumable detonation reaction engine and system

ABSTRACT

A detonation-reaction engine for attachment to a payload for propelling it at high velocities comprises a stage or stages, each having a sheet of explosive material, a sheet of material for restricting the propagation of the flame front, and a sheet of pressure-attenuating material encased in a lightweight, consumable structure. The attenuating material spreads out the pressure-time profile of the shock wave generated by the detonating explosive, and this somewhat reduces the intensity of the shock wave before it reaches the payload or the next engine stage. In this manner, the payload can be subjected to a series of successive detonation impulses from the successive stages occurring microseconds from each other in time, thereby adding successive increments of velocity to the payload.

United States Patent 1 Beichel et al.

[ 1 June 17, 1975 Aerojet-General Corporation, El Monte, Calif.

Filed: Apr. 22, 1971 Appl. No.: 136,368

Assignee:

References Cited UNITED STATES PATENTS 3/1933 Stolfa et al 60/250 6/1961Kimmel 60/255 2,990,684 7/1961 Cohen 60/255 3,053,182 9/1962 Christopherl02/2l.6

FOREIGN PATENTS OR APPLICATIONS 137,341 7/1952 Sweden ..60/250 582,42011/1946 United Kingdom 102/377 OTHER PUBLICATIONS Sultanoff, M. et a].,Third Symposium on Detona' tion," Princeton University, Sept., 1960, pp.520-526.

.lohansson, C. H. et al., Detonics of High Explosives," Academic Press,London, 1970, pp. 105-108.

Primary Examiner-C. J. Husar Assistant Examiner-Robert E. GarrettAttorney, Agent, or Firm-John L. McGannon; George M. Schwab [57]ABSTRACT A detonation-reaction engine for attachment to a payload forpropelling it at high velocities comprises a stage or stages, eachhaving a sheet of explosive material, a sheet of material forrestricting the propagation of the flame front, and a sheet ofpressure-attenuating material encased in a lightweight, consumablestructure. The attenuating material spreads out the pressure-timeprofile of the shock wave generated by the detonating explosive, andthis somewhat reduces the intensity of the shock wave before it reachesthe payload or the next engine stage. In this manner, the payload can besubjected to a series of successive detonation impulses from thesuccessive stages occurring microseconds from each other in time,thereby adding successive increments of velocity to the payload.

14 Claims, 7 Drawing Figures 1 CONSUMABLE DETONATION REACTION ENGINE ANDSYSTEM This invention relates to reaction engines, and more particularlyto such engines of the detonation-reaction type.

Reaction motors or engines comprising a pressure chamber wherein fuel isburned and an exhaust nozzle through which combustion products of theburned fuel are exhausted from the chamber to produce thrust are wellknown. It is also well known that explosives can be used to propelobjects over a wide velocity range, depending upon the method ofcontrolling the energy transfer to the object and upon the nature of theexplosive. It has also been known that detonated explosives canaccomplish such a propelling operation without the need of a pressurevessel or exhaust nozzle.

The transfer of energy from a detonating explosive to an object beingpropelled occurs when the detonation wave interacts with the interfaceof the explosive and the object to send a compression or chock shockinto the object. Pressures attained behind such shock waves areextremely high; for example, far beyond the ultimate strength of steel,which of course can involve the risk of damage to the object beingpropelled.

Objects of the present invention are to effect propulsion of an objector payload by explosive detonation in such a manner as to avoid damageor destruction to the payload, or of the propulsion engine itself beforehaving performed its function, and to obtain exceptionally highvelocities.

ln carrying out the invention, use is made of an engine stage behind theprojectile or payload comprising a sheet-like layer of explosive and ashock-waveattenuating means between the explosive layer and the payloador the next stage of the engine, as the case may be. According to apreferred feature of the invention, the engine is a plural ormulti-stage engine; hence, there can be achieved a staged rocket-likereaction engine using multiple energy pulses from detonating explosives,but requiring no pressure vessel nor exhaust nozzle.

The control, that is, the timing of the detonations, is important to thesuccessful practice of the invention. Such control is obtained bypreventing the detonation shock waves from one stage from causingdetonation of another stage, together with means for initiating thedetonator for the next unburned stage.

In order to achieve such detonating propulsion, particularly stageddetonation propulsion, the reaction engine is comprised of componentswhich filter the flame front resulting from a detonation, attenuate theshock wave to prevent uncontrolled or sympathetic detonation of theunburned explosive, and initiate the detonator for successive layers ofexplosive at regulated time intervals. This is carried out by use offilters, attenuators. and detonator igniters associated with the stages.

Another feature of the detonation-reaction engines according to thisinvention resides in their consumability. This results in reduction ofthe weight of the engine as it is consumed, allowing a higher velocityincrement to be applied to the payload.

The foregoing and other features of the invention will be betterunderstood from the following detailed description and the accompanyingdrawings of which:

FIG. 1 is a longitudinal cross-section view of a payload associated witha single-stage detonation-reaction engine according to this invention;

FIG. 2 is an end view of the payload and system of FIG. I viewed fromthe payload end;

FIG. 3 is a cross-section view of a device, similar to that of FIG. 1,provided with a two-stage detonationreaction engine according to thisinvention;

FIG. 4 illustrates a wrapping which may be applied around a deviceaccording to this invention;

FIG. 5 is a longitudinal cutaway view of a payload associated with afour-stage detonation-reaction engine according to this invention;

FIG. 6 is an end view of the system of FIG. 5 viewed from the propulsionend; and

FIG. 7 is an enlarged view of the encircled section of FIG. 5, moreclearly illustrating the relationship of the components of thefour-stage detonation-reaction engine with a wrapping applied thereonaccording to this invention.

In FIG. 1 there is shown an object or payload 10 to be propelled by adetonation reaction and is represented in the form of a solid cylinderof material; for example, a length of steel rod. The payload 10 or steelrod is illustrated as being circular when viewed from the end as in FIG.2 which shows the payload 10 in a plane perpendicular to thelongitudinal axis 11 of the rod. It should be understood that thepayload or projectile may take some other form as may be convenient ordesired. At one end of the rod or payload there is placed adetonation-reaction engine 12 comprising a circular disc or sheet 13 ofexplosive of substantially the same diameter as that of the end ofpayload to which it is attached. A detonator l4 aligned with thelongitudinal axis 11 of the payload has its forward end attached to therear side of the explosive 13, the detonator being detonable in any wellknown manner, such as an electrical means embodying the wires 15 whichlead to a source of electric current and which can be turned on by meansof a suitable switch (not shown) to initiate detonation. The front faceof the explosive disc 13 is covered by a sheet of suitable material toact as a filter for the flame front generated. The sheet 16 acts as afilter in that it permits the transmission of a shock wave generated bythe explosion of the explosive disc 13; however, it impedes thepropagation of the flame front. Between the front face of the sheet 16and the rear face of the payload 10 there is placed a circular disc 18of a slightly compressible material which acts as adetonation-wave-attenuator, the forward face of which is in contact withthe rear circular face of the payload 10.

The components of the detonation-reaction engine and the payload can beheld together in any suitable manner; for example, by use of adhesivesuch as an epoxy resin at the interfaces of each of the components l3,l4, l6, l8, and 10; or alternatively, by use of an external wrapper,such as a resinous sheet (not shown) around the cylindricalcircumference of the composite structure.

The sheet 13 may comprise practically any detonating explosive capableof being formed into or held within a sheet or disc, for example, PETN(pentaerythritol tetranitrate) I-IMX (l,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane), dynamite, nitrocellulose, nitroglycerin, or thelike; or the mixtures of explosives or explosive gases or liquidscapable of being encapsulated within the sheet structure or anuclear-type explosive. The filtering sheet 16 can be of a convenientmaterial, including solid metals or plastics, or the like. For example,aluminum foil capable of blocking or resisting the propagation of aflame front. The detonation-waveattenuating disc 18 may be of a suitablematerial providing an impedance to the propagation of the detonationwave which substantially mismatches the impedance of components 13 and16, thereby augmenting the attenuation. Suitable materials for theattenuating com ponent 18 include those which contain air spaces orgaps; for example, polyurethane foam or the like formed from suchmaterials as rubber or plastic. Such attenuating members tend tocompress under the impact of the shock wave or detonation wave, therebyhelping to produce a more planar and subdued pulse at the payload sideof the attenuating disc.

To operate the device, it may be placed on or in a suitable launcher ina manner similar to the launching of a rocket or alternatively within agun barrel or the like which may be open at both ends. Firing of thedetonator l4 detonates the explosive sheet or disc 13 which sends adetonation wave forwardly toward the projectile through the sheet 16 andthrough the attenuating disc 18 which reduces the harmful effects of thedetonation on the material of the projectile. The force of thedetonation wave nevertheless sends the projectile forwardly at highvelocity.

The effectiveness of propulsion by use of a detonation-reaction engineis greatly enhanced by use of multiple detonation stages in the engine.In this manner, only small velocity increments are imparted to thepayload with a reduction in stress on the structure and payload, andwith an increase in efficiency of explosive utilization. FIG. 3illustrates the use of a two-stage detonation reaction engine. In FIG.3, the payload is shown similar to the same numbered payload in FIG. 1.The first engine stage is somewhat similar to the engine of FIG. 1 inthat it comprises the explosive disc 13 detonable by a detonator l4 andthe detonation-wave-filtering sheet 16. Instead of a disc-shaped membersuch as 18 of FIG. 1, there is provided a member 19 which may be of thesame material as described for component 18 of FIG. I but formed with arearwardly protruding cylindrical portion 20 which abuts the sheet 16and around which there is placed an annular member 21 ofawaveattenuating material, such as described for member 18 of FIG. 1, andhaving the same outside diameter as the payload and other components ofthe engine.

The second stage of the engine shown in FIG. 3 is similar to the firststage of the engine in FIG. 1 in that it comprises the components l3,l6, and 18 behind the payload constructed and arranged similar to thesame numbered components in FIG. I. A detonator 22 placed at the rearside of the explosive 13 of this second stage serves to detonate thisexplosive. The detonator 22 for the second stage or successive stages ofthe engine is a type providing a predetermined time delay, as forexample, a solid propellant grain-to-lead azide delay train, milddetonating fuses, percussion sensitive detonators, or electric fieldgenerators.

In operation of the device of FIG. 3, detonation of the detonator 14detonates the first stage explosive 13 from which the detonation wavetravels forwardly through the filter sheet 16 and the attenuator 18,arriving at the detonator 22 wherein the detonator 22 is initiated andafter a very short interval of time the explosive 13 of the second stageis detonated.

FIG. 4 illustrates the use of a circumferential wrapping 23 around thecomponents of the device. Although it is shown with particular referenceto the single stage structure of FIG. I, it will be recognized that isapplies equally to multi-stage structures. The wrapping 23 may be of anysuitable material such as fiber glass or plastic material or the like,which may, if desired, be applied to the circumference by adhesive.Alternatively. the material 23 could be a shell such as a metallicshell, for example, aluminum. Use of such an exterior wrapping can, ifdesired, permit dispensing with use of adhesive between enginecomponents.

Reference is made to FIG. 5 wherein there is shown a four-stagedetonation-reaction engine. The payload 10 is shown similar to thesame-numbered payload in FIGS. 1 and 3. The first engine stage issomewhat similar to the engine of FIG. I in that it comprises theexplosive disc 13 detonable by the detonator I4 and the detonation wavefilter sheet 16. The detonator I4 is shown housed in a light-weightplastic foam structure 24. Instead of a sheet ofdetonation-wave-attenuating material 18, as shown in FIG. 1, there isprovided a honeycomb structure 17 in which the detonationattenuatingmaterial 18 is dispersed. The honeycomb structure 17 is a light-weightconsumable honeycomb structure and provides additional structuralstrength in addition to helping maintain control of the systemalignment. The detonator 22 shown in FIG. 5 may be the same as thedetonator 22 shown in FIG. 3.

Reference is made to FIG. 6 wherein there is illustrated an end-view ofthe system as viewed from the propulsion end. The detonator 14 is shownin its housing of a light-weight plastic foam structure 24. In thecutaway portion of FIG. 6 there is shown the honeycomb structure 17 inwhich the detonatiomwaveattenuating material is dispersed.

FIG. 7 is an enlarged view of the encircled area of FIG. 5. This FIG. 7illustrates the sheef of explosive l3 and the sheet of filter material16 being disposed between sections of honeycomb structure 17 in whichdetonation-wave-attenuating material 18 is dispersed. FIG. 7 also showsthe use of the circumferential wrapping 23 around the components of theengine.

In operation of the device of FIG. 5, detonation of the detonator l4detonates the first stage explosive 13 from which the detonation wavetravels forwardly through the filter sheet 16 and the attenuatormaterial 18 arriving at the detonator 22. The detonator 22 is initiatedand after a very short interval of time the explosive 13 of the secondstage is detonated. This procedure is repeated as each stage isdetonated in succession. In this manner, only small velocity incrementsare imparted to the payload 10 with a reduction in stress on thestructure and the payload, and with an increase in efficiency ofexplosive utilization.

It will be recognized that any number of stages may be used in theengine and it will be ordinarily desirable to provide many more stagesthan the two or four illustrated in the drawings. The first andsubsequent stages of an engine having more than four stages would besimilar to the device illustrated in FIG. 5. It becomes apparent tothose versed in the art that the last stage of a multiple-stage enginemay be modified in that the detonator for the last stage would notrequire the timing control mechanism as necessary in the intermediatestages.

In the operation ofa unit having a multi-stage engine, the detonationsof the successive stages will occur in rapid succession and thedetonation action will appear continuous since there will be only amatter of microseconds between successive detonations. Each successivedetonation will give the device an added increment of forward velocity,resulting in an extremely high endvelocity for the payload. Thedetonation-reaction engine itself is self-consuming while thedetonations are occurring; hence there is a continuous lightening up ofthe device as the detonations progressresulting in less and less mass tobe propelled, which is advantageous in obtaining maximum velocity forthe payload. From the foregoing description, it becomes apparent tothose with skill in the art that the detonation-reaction engine hereindescribed possesses the inherent capability of permitting a shutdown andrestart being designed into it should a specific application requirethis feature.

The payload can take any of many useful forms, such as, but not limitedto, structural piles, artillery shells, rockets, including soundingrockets and missiles,

The embodiments shown in the drawings and described in the descriptionare given by way of example and it will be apparent to those skilled inthe art that modifications and variations may be made without departingfrom the spirit and scope of the appended claims.

What is claimed is:

l. A consumable detonation-reaction engine adapted to be mounted on theend of a payload, said engine comprising a plurality of stages arrangedin tandem along an axis extending in the direction of forward impulse,each said stage comprising:

an explosive member;

means adapted to said explosive member for detonating the explosive;

a flamc-front-filtering means in front of the explosive member forrestricting propagation of the flame front through it in the forwarddirection; and

a shock-wave-attenuating means in front of the filtering means andcomprising a structure of air impregnated foam material having apredetermined compressibility substantially mismatching thecompressibility of the explosive member and the flame front filteringmeans for reducing the impulse of the shock wave passing forwardlythrough it and more evenly planarly distributing said impulse.

2. An engine in accordance with claim 1 wherein the means for detonatingsaid explosive member of each stage sequentially from the initial stageis positioned at its respective stage to receive the impulse of thedetonation wave resulting from the detonation of the adjacent rearwardstage as said wave passes forwardly through the attenuator of saidadjacent rearward stage.

3. An engine according to claim 2 wherein the detonating means for eachstage subsequent to the initial stage includes a delay train which isinitiated by the impulse of the detonation wave resulting from theexplosion of the adjacent rearward stage.

4. An engine according to claim 1 wherein the detonating means isfurther adapted so that the detonation from the explosive of each stageexcepting the forwardmost stage initiates the detonation of theexplosive of the adjacent forward stage and the impulse from thedetonation of each stage is transmitted forward and is applied againstthe rearward face of the payload, the detonations occurring in rapidsuccession while the payload is being propelled forwardly and while thestages of the engine are being consumed in succession.

5. An engine in accordance with claim 1 wherein said explosive member isin the form of a sheet of explosive and said filtering means is in theform of a layer of material covering the forward surface of theexplosive sheet and the attenuating means comprises ashockwave-attenuating material covering the forward surface of thefilter, and the payload is mounted to the engine to abut the forwardsurface of the attenuating means of the most forward stage.

6. An engine in accordance with claim 1 wherein said filtering means isa sheet of solid material having means to permit restrictive passage ofthe flame front resulting from detonation of the explosive.

7. An engine in accordance with claim 1 wherein means is providedholding the explosive member, the filter means, and the attenuator meansin contact with each other.

8. An engine in accordance with claim 1 wherein the payload and stagesof the engine are cylindrical.

9. An engine in accordance with claim 1 wherein saidshock-wave-attenuating means is encased in a lightweight, consumablehoneycomb structure.

10. A consumable detonation-reaction engine having at least one stagecomprising: a sheet of explosive material; a filter of flame-resistantmaterial covering the forward surface of the explosive sheet; and alayer of shock-wave-attenuating material covering the forward surface ofthe filter, said shock-wave-attenuating material comprisingair-impregnated foam material, the compressibility of which issubstantially greater than the compressibility of the explosive materialand the filter whereby the flame front from the detonation of theexplosive layer is impeded by said filter but the shock wave thereofpasses through said filter, said shock wave being attenuated by theshock-waveattenuating material to reduce the peak impulse resulting fromthe detonation of said stage.

11. An engine in accordance with claim 10 wherein said filter layerincludes means for permitting restricted passage of the flame fronttherethrough.

12. An engine in accordance with claim 11 wherein saidshock-wave-attenuating material is encased in a light-weight consumablehoneycomb structure.

13. A consumable detonation-reaction engine adapted to be mounted on theend of a payload, said engine comprising a plurality of stages arrangedin tandem along an axis extending in the direction of forward impulse,each said stage comprising an explosive member, a flame-front filteringmeans in front of the explosive member for restricting propagation ofthe flamefront in the forward direction, a shock-waveattenuating meansin front of the filtering means and comprising a foam material encasedin a light-weight consumable honeycomb structure, the compressibility ofsaid foam material being substantially greater than the compressibilityof the explosive member and the filtering means for reducing the impulseof the shock wave passing forwardly through it; means adapted to theexplosive member of the rear-most stage for detonating the explosive ofsaid rear-most stage; and means for detonating the explosive member ofeach other stage, said later detonating means being activated by theimpulse of the detonation wave resulting from the explosion of theadjacent rearward stage so that the detonation of the explosive of eachstage initiates the detonation of the explosive of each adjacent forwardstage and the detonations occur in rapid succession to propel thepayload forwardly.

14. An engine according to claim 1 wherein said compressible materialcomprises air-impregnated foam encapsulated in a light-weight consumablehoneycomb structure.

t: t I i t

1. A consumable detonation-reaction engine adapted to be mounted on theend of a payload, said engine comprising a plurality of stages arrangedin tandem along an axis extending in the direction of forward impulse,each said stage comprising: an explosive member; means adapted to saidexplosive member for detonating the explosive; a flame-front-filteringmeans in front of the explosive member for restricting propagation ofthe flame front through it in the forward direction; and ashock-wave-attenuating means in front of the filtering means andcomprising a structure of air impregnated foam material having apredetermined compressibility substantially mismatching thecompressibility of the explosive member and the flame front filteringmeans for reducing the impulse of the shock wave passing forwardlythrough it and more evenly planarly distributing said impulse.
 2. Anengine in accordance with claim 1 wherein the means for detonating saidexplosive member of each stage sequentially from the initial stage ispositioned at its respective stage to receive the impulse of thedetonation wave resulting from the detonation of the adjacent rearwardstage as said wave passes forwardly through the attenuator of saidadjacent rearward stage.
 3. An engine according to claim 2 wherein thedetonating means for each stage subsequent to the initial stage includesa delay train which is initiated by the impulse of the detonation waveresulting from the explosion of the adjacent rearward stage.
 4. Anengine according to claim 1 wherein the detonating means is furtheradapted so that the detonation from the explosive of each stageexcepting the forwardmost stage initiates the detonation of theexplosive of the adjacent forward stage and the impulse from thedetonation of each stage is transmitted forward and is applied againstthe rearward face of the payload, the detonations occurring in rapidsuccession while the payload is being propelled forwardly and while thestages of the engine are being consumed in succession.
 5. An engine inaccordance with claim 1 wherein said explosive member is in the form ofa sheet of explosive and said filtering means is in the form of a layerof material covering the forward surface of the explosive sheet and theattenuating means comprises a shock-wave-attenuating material coveringthe forward surface of the filter, and the payload is mounted to theengine to abut the forward surface of the attenuating means of the mostforward stage.
 6. An engine in accordance with claim 1 wherein saidfiltering means is a sheet of solid material having means to permitrestrictive passage of the flame front resulting from detonation of theexplosive.
 7. An engine in accordance with claim 1 wherein means isprovided holding the explosive member, the filter means, and theattenuator means in contact with each other.
 8. An engine in accordancewith claim 1 wherein the payload and stages of the engine arecylindricAl.
 9. An engine in accordance with claim 1 wherein saidshock-wave-attenuating means is encased in a light-weight, consumablehoneycomb structure.
 10. A consumable detonation-reaction engine havingat least one stage comprising: a sheet of explosive material; a filterof flame-resistant material covering the forward surface of theexplosive sheet; and a layer of shock-wave-attenuating material coveringthe forward surface of the filter, said shock-wave-attenuating materialcomprising air-impregnated foam material, the compressibility of whichis substantially greater than the compressibility of the explosivematerial and the filter whereby the flame front from the detonation ofthe explosive layer is impeded by said filter but the shock wave thereofpasses through said filter, said shock wave being attenuated by theshock-wave-attenuating material to reduce the peak impulse resultingfrom the detonation of said stage.
 11. An engine in accordance withclaim 10 wherein said filter layer includes means for permittingrestricted passage of the flame front therethrough.
 12. An engine inaccordance with claim 11 wherein said shock-wave-attenuating material isencased in a light-weight consumable honeycomb structure.
 13. Aconsumable detonation-reaction engine adapted to be mounted on the endof a payload, said engine comprising a plurality of stages arranged intandem along an axis extending in the direction of forward impulse, eachsaid stage comprising an explosive member, a flame-front filtering meansin front of the explosive member for restricting propagation of theflame-front in the forward direction, a shock-wave-attenuating means infront of the filtering means and comprising a foam material encased in alight-weight consumable honeycomb structure, the compressibility of saidfoam material being substantially greater than the compressibility ofthe explosive member and the filtering means for reducing the impulse ofthe shock wave passing forwardly through it; means adapted to theexplosive member of the rear-most stage for detonating the explosive ofsaid rear-most stage; and means for detonating the explosive member ofeach other stage, said later detonating means being activated by theimpulse of the detonation wave resulting from the explosion of theadjacent rearward stage so that the detonation of the explosive of eachstage initiates the detonation of the explosive of each adjacent forwardstage and the detonations occur in rapid succession to propel thepayload forwardly.
 14. An engine according to claim 1 wherein saidcompressible material comprises air-impregnated foam encapsulated in alight-weight consumable honeycomb structure.